1. Field of the Invention
The present invention relates to a system for infusion of medicine into the body of a patient of the type including an implantable infusion apparatus containing a dosing unit with a reservoir for the medicine and a medicine delivery pump for pumping doses of medicine from the reservoir into the patient, a sensor for sensing a parameter of the patient for controlling the dosing of medicine according to the sensed parameter, the dosing unit and the sensor being galvanically separable (i.e. no direct path for electric current flow) and each being provided with separate telemetering communication means for communication with an external controller.
2. Description of the Prior Art
Systems of this type for infusion of, e.g., insulin are known, see e.g. U.S. Pat. No. 4,494,950 and W. Schubert et al, "An implantable artificial pancreas", Medical and Biological Engineering & Computing, 1980, 18, pp. 527-537. In the latter document an artificial implantable pancreas is described in which, in a first mode of operation, a glucose sensor transmits the actual blood glucose level to a control unit, in which the amount of insulin to be infused is calculated on the basis of patient specific parameters, recorded in a program memory and corresponding control signals for a dosing unit are determined by a control algorithm. If no sensor is used or if the sensor employed fails the dosing unit is controlled, in a second mode of operation, by a stored dosing program. Thus, the first mode of operation corresponds to a closed control loop and the second mode of operation to an open control loop.
In U.S. Pat. No. 4,543,955 a system is also described having an implantable physiological sensor for controlling an implantable device in response to changes in the parameter sensed by the sensor. The implantable device can be a heart pacing device, a drug infusion pump or another device interacting with a human body. In this system the sensor directly communicates with the device by conductors or a telemetry link. A heart pacing system of this type is also described in European Application 0,317,986.
Considerable efforts have been made in developing implantable closed loop systems for the control of blood glucose in which a sensor continuously monitors the glucose level and optimally controls the infusion of insulin into the patient. The creation of such an implanted system, which is completely safe to the patient, however, still poses significant difficulties.